PROJECT SUMMARY Improved control over synovial inflammation is anticiapted to slow bone erosion and reduce the risk of fractures and pain. However, even potent anti-inflammatory strategies such as blockade of TNF or IL6R, only show limited bone repair, suggesting that suppressing inflammation is insufficient to restore osteo-immune balance. Some current and emerging therapies succeed in slowing erosion by suppressing osteoclast activity, but fail to significantly stimulate bone formation. Further, these biologics are not targeted for accumulation at inflammed joints, thus are administered systemically, enhancing the likelihood of serious infection. For therapeutics to succeed in promoting bone repair, they likely must balance levels and activity of several proinflammatory cells to disrupt their interaction with osteoclasts, and promote osteoblast maturation or activity. Thus a critical unmet need for inflammatory bone loss is an intervention that can restore eroded bone through rebalancing immune:bone cell homeostasis in order to reduce fracture risk and improve quality of life for patients. Recent data points to a novel use for cytokine Interleukin-27 (IL-27) as a regulator of immune and bone cell balance, as it reduces osteoclastogenesis and promotes osteoblast proliferation and maturation. Also, IL-27 suppresses activities of immune and synovial cells mediating the onset and maintenance of inflammation and also has anti-angiogenic activity. Current strategies for delivering recombinant (r)IL-27 are systemic and lack specificity to immune or bone cells, and moreover are unable to sustain therapeutic effects over time due to rapid clearance. We propose to examine whether a targeted IL-27, delivered using a sustained expression system, will be effective in promoting bone repair and reducing inflammation in joints using a collagen-antibody induced arthritis (CAIA) model. Intraarticular sonoporation gene delivery (sonodelivery) will transfer into the joints a nanoplex of polymer and plasmid DNA encoding targeted IL-27 to reduce inflammation and promote bone repair. Our hypothesis is that optimizing delivery and targeting of IL-27 to joints will facilitate endogenous bone repair by re-balancing osteo-immune homeostasis. To test this hypothesis, we propose 1) To achieve therapeutic levels of cytokine in joints, we will optimize IL-27 intra-articular sonodelivery; 2) To enhance cytokine retention in bone and promote endogenous bone repair, we will promote ligand-mediated targeting of IL-27 to bone cells or matrix, and 3) To enhance cytokine retention at the pannus and synovial lining and facilitate bone repair, we will promote ligand-mediated targeting of IL-27 to inflammatory and immune cells. We anticipate that this simple sonodelivery strategy will provide an efficient means to restore eroded bone in articulations affected by rheumatoid arthritis (RA). IL-27 is unique in its ability to simultaneously inhibit inflammation and promote bone repair. This approach is exciting in that we envision applications across numerous conditions characterized by bone loss.